The invention relates to a tube-shaped sputtering target having a carrier tube and an indium-based sputtering material arranged on the carrier tube.
Indium tube targets are used, for example, for coating CuInGa absorber layers for thin layer photovoltaic cells based on CuInGaS2 or CuInGaSe2 (also referred to as “CIGS”). Indium sputtering is often associated with the formation of needle-shaped structures on the surface of the sputtering target, which lead to different sputtering rates and thus uneven thickness of layers as a function of grain orientation (M. Weigert, “The Challenge of CIGS Sputtering,” Heraeus Thin Film Materials magazine, No. 11, April 2008).
Thus far, the corresponding tube targets have been produced by a simple casting process, as is described, for example, in European Patent EP 1 186 682 B1. Owing to the metal needing to be very pure (99.99 to 99.999%) for the CIGS application, the sputtering targets have a very coarse structure, which may then lead to the problems mentioned above.